1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>basic_seq_packet_socket::native_non_blocking (2 of 3 overloads)</title> 5<link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../../../boost_asio.html" title="Boost.Asio"> 8<link rel="up" href="../native_non_blocking.html" title="basic_seq_packet_socket::native_non_blocking"> 9<link rel="prev" href="overload1.html" title="basic_seq_packet_socket::native_non_blocking (1 of 3 overloads)"> 10<link rel="next" href="overload3.html" title="basic_seq_packet_socket::native_non_blocking (3 of 3 overloads)"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="overload1.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../native_non_blocking.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../boost_asio.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="overload3.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h5 class="title"> 27<a name="boost_asio.reference.basic_seq_packet_socket.native_non_blocking.overload2"></a><a class="link" href="overload2.html" title="basic_seq_packet_socket::native_non_blocking (2 of 3 overloads)">basic_seq_packet_socket::native_non_blocking 28 (2 of 3 overloads)</a> 29</h5></div></div></div> 30<p> 31 <span class="emphasis"><em>Inherited from basic_socket.</em></span> 32 </p> 33<p> 34 Sets the non-blocking mode of the native socket implementation. 35 </p> 36<pre class="programlisting">void native_non_blocking( 37 bool mode); 38</pre> 39<p> 40 This function is used to modify the non-blocking mode of the underlying 41 native socket. It has no effect on the behaviour of the socket object's 42 synchronous operations. 43 </p> 44<h6> 45<a name="boost_asio.reference.basic_seq_packet_socket.native_non_blocking.overload2.h0"></a> 46 <span class="phrase"><a name="boost_asio.reference.basic_seq_packet_socket.native_non_blocking.overload2.parameters"></a></span><a class="link" href="overload2.html#boost_asio.reference.basic_seq_packet_socket.native_non_blocking.overload2.parameters">Parameters</a> 47 </h6> 48<div class="variablelist"> 49<p class="title"><b></b></p> 50<dl class="variablelist"> 51<dt><span class="term">mode</span></dt> 52<dd><p> 53 If <code class="computeroutput">true</code>, the underlying socket is put into non-blocking 54 mode and direct system calls may fail with <code class="computeroutput">boost::asio::error::would_block</code> 55 (or the equivalent system error). 56 </p></dd> 57</dl> 58</div> 59<h6> 60<a name="boost_asio.reference.basic_seq_packet_socket.native_non_blocking.overload2.h1"></a> 61 <span class="phrase"><a name="boost_asio.reference.basic_seq_packet_socket.native_non_blocking.overload2.exceptions"></a></span><a class="link" href="overload2.html#boost_asio.reference.basic_seq_packet_socket.native_non_blocking.overload2.exceptions">Exceptions</a> 62 </h6> 63<div class="variablelist"> 64<p class="title"><b></b></p> 65<dl class="variablelist"> 66<dt><span class="term">boost::system::system_error</span></dt> 67<dd><p> 68 Thrown on failure. If the <code class="computeroutput">mode</code> is <code class="computeroutput">false</code>, 69 but the current value of <code class="computeroutput">non_blocking()</code> is <code class="computeroutput">true</code>, 70 this function fails with <code class="computeroutput">boost::asio::error::invalid_argument</code>, 71 as the combination does not make sense. 72 </p></dd> 73</dl> 74</div> 75<h6> 76<a name="boost_asio.reference.basic_seq_packet_socket.native_non_blocking.overload2.h2"></a> 77 <span class="phrase"><a name="boost_asio.reference.basic_seq_packet_socket.native_non_blocking.overload2.example"></a></span><a class="link" href="overload2.html#boost_asio.reference.basic_seq_packet_socket.native_non_blocking.overload2.example">Example</a> 78 </h6> 79<p> 80 This function is intended to allow the encapsulation of arbitrary non-blocking 81 system calls as asynchronous operations, in a way that is transparent 82 to the user of the socket object. The following example illustrates how 83 Linux's <code class="computeroutput">sendfile</code> system call might be encapsulated: 84 </p> 85<pre class="programlisting">template <typename Handler> 86struct sendfile_op 87{ 88 tcp::socket& sock_; 89 int fd_; 90 Handler handler_; 91 off_t offset_; 92 std::size_t total_bytes_transferred_; 93 94 // Function call operator meeting WriteHandler requirements. 95 // Used as the handler for the async_write_some operation. 96 void operator()(boost::system::error_code ec, std::size_t) 97 { 98 // Put the underlying socket into non-blocking mode. 99 if (!ec) 100 if (!sock_.native_non_blocking()) 101 sock_.native_non_blocking(true, ec); 102 103 if (!ec) 104 { 105 for (;;) 106 { 107 // Try the system call. 108 errno = 0; 109 int n = ::sendfile(sock_.native_handle(), fd_, &offset_, 65536); 110 ec = boost::system::error_code(n < 0 ? errno : 0, 111 boost::asio::error::get_system_category()); 112 total_bytes_transferred_ += ec ? 0 : n; 113 114 // Retry operation immediately if interrupted by signal. 115 if (ec == boost::asio::error::interrupted) 116 continue; 117 118 // Check if we need to run the operation again. 119 if (ec == boost::asio::error::would_block 120 || ec == boost::asio::error::try_again) 121 { 122 // We have to wait for the socket to become ready again. 123 sock_.async_wait(tcp::socket::wait_write, *this); 124 return; 125 } 126 127 if (ec || n == 0) 128 { 129 // An error occurred, or we have reached the end of the file. 130 // Either way we must exit the loop so we can call the handler. 131 break; 132 } 133 134 // Loop around to try calling sendfile again. 135 } 136 } 137 138 // Pass result back to user's handler. 139 handler_(ec, total_bytes_transferred_); 140 } 141}; 142 143template <typename Handler> 144void async_sendfile(tcp::socket& sock, int fd, Handler h) 145{ 146 sendfile_op<Handler> op = { sock, fd, h, 0, 0 }; 147 sock.async_wait(tcp::socket::wait_write, op); 148} 149</pre> 150</div> 151<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 152<td align="left"></td> 153<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M. 154 Kohlhoff<p> 155 Distributed under the Boost Software License, Version 1.0. (See accompanying 156 file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) 157 </p> 158</div></td> 159</tr></table> 160<hr> 161<div class="spirit-nav"> 162<a accesskey="p" href="overload1.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../native_non_blocking.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../boost_asio.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="overload3.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 163</div> 164</body> 165</html> 166
